The goal of this project is to identify characteristics of intracellular trafficking of dopamine receptors in mammalian cells. Dopamine receptor subtypes and genetic variants from a subfamily of g protein- coupled receptors sharing highly functional properties, yet subcellular receptor processing mechanisms are not well understood. Intracellular trafficking mechanisms distinguish the regulation of other classes of functionally similar G protein-coupled receptor by influencing their number and their functional state. However, no previous studies have directly examined the subcellular regulation and trafficking of dopamine receptors, or how the trafficking of individual cloned subtypes or variants may differ. These studies will provide new information regarding the cell biology of this class of receptor. In addition, structure-function data generated from the proposed experiments will be essential for understanding the physiological roles of trafficking operations as well as the fundamental protein-protein interactions that mediate receptor trafficking. The following specific aims will be addressed: 1) Direct examination of the subcellular distribution of cloned D1, D2 and D4 dopamine receptors and genetic variants in transfected cells using immunochemical techniques. 2) Determine the effects of agonist and antagonist ligands on the subcellular distribution and trafficking of cloned dopamine receptors. 30 Define receptor domains which mediate and regulate dopamine receptor trafficking using site-directed mutagenesis, focusing on putative subtype- and variant-specific differences in receiptor trafficking. 4) Examine the functional effects of receptor trafficking mutations on cell signaling.